1、MSS SP-75-2014 High-Strength, Wrought, Butt-Welding Fittings Standard Practice Developed and Approved by the Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. 127 Park Street, NE Vienna, Virginia 22180-4602 Phone: (703) 281-6613 Fax: (703) 281-6671 E-mail: standardsmss-h
2、q.org www.mss-hq.org MSS STANDARD PRACTICE SP-75i This MSS Standard Practice was developed under the consensus of the MSS Technical Committee 113 and the MSS Coordinating Committee. Input from the user community and the Regulatory body responsible for pipeline safety compliance was requested and the
3、 task group assigned to revising this Standard Practice had very important input from these groups in preparing this edition of SP-75. The content of this Standard Practice is the resulting efforts of competent and experienced volunteers to provide an effective, clear, and non-exclusive standard tha
4、t will benefit the industry as a whole. This MSS Standard Practice describes minimal requirements and is intended as a basis for common practice by the manufacturer, the user, and the general public. The existence of an MSS Standard Practice does not in itself preclude the manufacture, sale, or use
5、of products not conforming to the Standard Practice. Mandatory conformance to this Standard Practice is established only by reference in other documents such as a code, specification, sales contract, or public law, as applicable. MSS has no power, nor does it undertake, to enforce or certify complia
6、nce with this document. Any certification or other statement of compliance with the requirements of this Standard Practice shall not be attributable to MSS and is solely the responsibility of the certifier or maker of the statement. “Unless indicated otherwise within this MSS Standard Practice, othe
7、r standards documents referenced to herein are identified by the date of issue that was applicable to this Standard Practice at the date of approval of this MSS Standard Practice (see Annex A). This Standard Practice shall remain silent on the validity of those other standards of prior or subsequent
8、 dates of issue even though applicable provisions may not have changed.” By publication of this Standard Practice, no position is taken with respect to the validity of any potential claim(s) or of any patent rights in connection therewith. MSS shall not be held responsible for identifying any patent
9、 rights. Users are expressly advised that determination of patent rights and the risk of infringement of such rights are entirely their responsibility. In this Standard Practice, all text, notes, annexes, tables, figures, and references are construed to be essential to the understanding of the messa
10、ge of the standard, and are considered normative unless indicated as “supplemental”. All appendices, if included, that appear in this document are construed as “supplemental”. Note that supplemental information does not include mandatory requirements. This Standard Practice has been substantially re
11、vised from the previous 2008 edition. It is suggested that if the user is interested in knowing what changes have been made, that direct page by page comparison should be made of this document and that of the previous edition. Non-toleranced dimensions in this Standard Practice are nominal unless ot
12、herwise specified. Excerpts of this Standard Practice may be quoted with permission. Credit lines should read Extracted from MSS SP-75-2014 with permission of the publisher, Manufacturers Standardization Society of the Valve and Fittings Industry. Reproduction and/or electronic transmission or disse
13、mination is prohibited under copyright convention unless written permission is granted by the Manufacturers Standardization Society of the Valve and Fittings Industry Inc. All rights reserved. Originally Approved: September 1970 Originally Published: November 1970 Current Edition Approved: April 201
14、4 Current Edition Published: September 2014 MSS is a registered trademark of Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. Copyright , 2014 by Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. Printed in U.S.A. MSS STANDARD PRACTICE SP-75
15、ii TABLE OF CONTENTS SECTION PAGE 1 SCOPE 1 2 PRESSURE RATINGS . 1 3 SIZE 2 4 DESIGN PROOF-TEST . 2 5 HYDROSTATIC TESTING . 3 6 MATERIALS 3 7 CHEMICAL COMPOSITION . 3 8 TENSILE PROPERTIES 4 9 HEAT TREATMENT . 5 10 TRANSVERSE GUIDED-WELD BEND-TESTS . 5 11 NOTCH-TOUGHNESS PROPERTIES . 6 12 FITTING DIM
16、ENSIONS . 6 13 TOLERANCES FOR WELDING FITTINGS 6 14 MANUFACTURE 7 15 NONDESTRUCTIVE EXAMINATION (NDE) 8 16 INSPECTION . 8 17 MARKING . 9 TABLE 1 Maximum Limit of Chemical Elements 14 2 Tensile Requirements 14 3 Tolerances . 15 4 Dimensions of Long-Radius Elbows 16 5 Dimensions of 3R Elbows . 17 6 Di
17、mensions of Straight Tees . 18 7 Dimensions of Reducing Outlet Tees 19 8 Dimensions of Caps . 22 9 Dimensions of Reducers 23 FIGURE 1 Recommended Bevel for Wall Thicknesses (T) at End of Fitting, 0.75 in. or Less 11 2 Recommended Bevel for Wall Thicknesses (T) at End of Fitting, Greater than 0.75 in
18、. . 11 3 Acceptable Design for Unequal Wall Thickness 12 4 Traverse Face and Root-Bend Test Specimens . 12 5 Guided-Bend Test Jig 13 X2-1 Longitudinal-Bead Underbead Cracking Test Specimen 28 ANNEX A Referenced Standards and Applicable Dates . 25 APPENDIX X1 Supplementary Requirements 26 X2 Longitud
19、inal-Bead Underbead Cracking Test 28 X3 Recommendations for Segmenting 29 MSS STANDARD PRACTICE SP-751 1. SCOPE 1.1 This Standard Practice covers factory-made, seamless and electric welded carbon and low-alloy steel, butt-welding fittings for use in high pressure gas and oil transmission and distrib
20、ution systems; including pipelines, compressor stations, metering and regulating stations, and mains. 1.2 This Standard Practice governs dimensions, tolerances, ratings, testing, materials, chemical and tensile properties, heat treatment, notch toughness properties, manufacture, inspection and marki
21、ng for high-strength, butt-welding fittings NPS 60 and smaller. Dimensional requirements for NPS 14 and smaller are provided by reference to ASME B16.9. 1.3 The term “welding fittings” applies to butt-welding fittings such as elbows, segments of elbows, return bends, caps, tees, single or multiple-o
22、utlet extruded headers, reducers, and extensions and transition sections(1).Girth weld requirements are outside the scope of this Standard Practice and are covered by the applicable ASME B31 Code for Pressure Piping and/or customer specifications. 1.4 Fittings may be made to special dimensions, size
23、s, shapes, and tolerances, or of wrought materials other than those covered by this Standard Practice by agreement between the manufacturer and the purchaser. When such fittings meet all other stipulations of this Standard Practice they shall be considered as being in partial compliance therewith, p
24、roviding they are appropriately marked. 1.4.1 Fittings manufactured in partial compliance, as provided in Section 1.4, shall be identified with “Part” following the respective grade designation. NOTE: (1) Lengths of extensions and transitions as agreed upon by purchaser and manufacturer. 2. PRESSURE
25、 RATINGS 2.1 The allowable internal-pressure ratings for pipe fittings designed in accordance with this Standard Practice shall be calculated as for straight seamless pipe (or welded pipe with a joint efficiency factor of 1.0) of equivalent grade, diameter and wall thickness in accordance with the r
26、ules established in the applicable sections of ASME B31 Codes. 2.2 All fittings produced in accordance with this Standard Practice shall be designed to withstand a field hydrostatic test pressure, after installation, at a pressure level equivalent to that required to develop a hoop stress equal to t
27、he specified minimum yield strength for pipe of equivalent grade and wall thickness based on Barlows Formula, without failure, leakage, or impairment of serviceability. Barlows formula is defined as: DStP2 Where: P = internal design pressure, psig; S = specified minimum yield strength of the pipe, p
28、si; t = nominal wall thickness of the pipe, inches; D = outside diameter of the pipe, inches. 2.3 By agreement between the manufacturer and the purchaser, fittings may be tested at a higher pressure providing the manufacturer is notified of the test pressure to be used. 2.4 The design shall take int
29、o consideration performance requirements prescribed above as well as additional factors dictated by the shape of the part. 2.5 The design of fittings may be established by mathematical analyses contained in nationally recognized pressure vessel or piping codes or, at the manufacturers option, by pro
30、of testing in accordance with Section 4. HIGH-STRENGTH, WROUGHT, BUTT-WELDING FITTINGS MSS STANDARD PRACTICE SP-752 The design of fittings that cannot be qualified by mathematical analyses shall be established by proof testing in accordance with Section 4. 3. SIZE The nominal size of the fittings re
31、fers to the nominal O.D. of the pipe to which it is attached. 4. DESIGN PROOF-TEST 4.1 Proof tests shall be made as set forth in this Standard Practice when the manufacturer chooses proof testing to qualify the fitting design. The proof test shall be based on the computed burst pressure of the fitti
32、ng and its connecting piping as defined in Section 4.3. A factory-made segmented elbow that has a proof test on a geometrically similar 90-deg elbow need not be tested separately. 4.2 Test Assembly Requirements: 4.2.1 Fittings that have the same basic design configuration and method of manufacture s
33、hall be selected from production for testing and shall be identified as to material, grade and lot, including heat treatment. They shall be inspected for dimensional compliance to this Standard Practice. 4.2.2 Straight seamless or welded pipe whose calculated bursting strength is at least as great a
34、s the proof test pressure as calculated in Section 4.3, shall be welded to each end of the fitting to be tested. Pipe sections may have the nominal wall greater than the thickness indicated by the fitting markings. That greater thickness shall not exceed 1.5 times the nominal pipe wall thickness of
35、the pipe that the fitting marking identifies. Any internal misalignment greater than 0.06 in. shall be reduced by taper boring at a slope not exceeding 1:3 (18). Any other unequal wall welding preparation shall be in accordance with Figure 3. The minimum length of pipe sections for closures shall be
36、 one-half pipe O.D. for greater than NPS 14 and one pipe O.D. for NPS 14 and smaller. 4.3 The test fluid shall be water or other liquid. Hydrostatic pressure shall be applied to the assembly. At least three (3) proof tests for each fitting, joint size, or configuration are recommended. The testing f
37、actor, f, based on the number of specimen tests performed in the table below is used in the computed test equations: Number of Tests Testing Factor, f 1 1.10 2 1.05 3 1.00 NOTE: Tests of similarly proportioned fittings that meet the requirements specified in Section 4.4 may be combined to establish
38、the test factor applied to a set of fittings. The test shall be taken to rupture or held at or above the computed minimum proof pressure for a period of at least three (3) minutes. The test is successful if for each of the tests, the fitting withstands without rupture a proof test pressure at least
39、equal to the computed minimum: P = 2 f St/D Where: D = specified outside diameter of pipe; f = testing factor from table listed in Section 4.3; P = computed minimum proof test pressure for fitting; S = actual tensile strength of the test fitting, determined on a specimen representative of the test f
40、itting, which shall meet the tensile strength requirements of the applicable material of Section 6; t = nominal pipe wall thickness of the pipe that the fitting marking identifies. 4.4 It is not necessary to conduct an individual test of fittings with all combinations of sizes, wall thicknesses, and
41、 materials. A successful proof test on one representative fitting may represent others to the extent described in Sections 4.4.1, 4.4.2, 4.4.3, and 4.4.4. 4.4.1 One test fitting may be used to qualify similarly proportioned fittings with a size range from one-half to twice that for the tested fittin
42、g. The test of a non-reducing fitting qualifies reducing fittings of the same pattern. The test of a reducing fitting qualifies reductions to smaller sizes. MSS STANDARD PRACTICE SP-753 4.4.2 One test fitting may be used to qualify similarly proportioned fittings with tD ranges from one-half to thre
43、e times that for the tested fitting. 4.4.3 The pressure retaining capacity of a geometrically identical fitting made of various grades of steel as listed in Section 6 will be directly proportional to the tensile properties of the materials, provided the yield-to-tensile ratio is 0.90 or less. Theref
44、ore, it is necessary to test only a single material in a representative fitting to prove the design of the fitting. For yield-to-tensile ratios greater than 0.84, additional testing should be considered. 4.4.4 A test on a prototype elbow qualifies elbows having longer radii than the test fitting pro
45、viding they qualify under Sections 4.4.1 and 4.4.3. 4.5 The manufacturer shall have a quality control (QC) program that verifies the manufacturing process used and ensures that the resulting geometry of the fittings or joints manufactured reasonably conforms to the geometries tested. The QC program
46、shall control the manufacturing drawings and maintain the QC records showing conformance to these drawings. Tests made in accordance with and at the time of previous editions of this test are not intended to be nullified by the changes made in this editions test procedure and requirement. Whenever a
47、 significant change is made in the geometry or method of manufacture, the manufacturer shall either retest the new production or show by analysis that the change would not affect the results of prior tests. 4.6 A report of the testing for each test assembly shall be prepared and shall include: (a) D
48、escription of the test, including the number of tests and f factor used to establish the target proof test; (b) Instrumentation and methods of calibrations used; (c) Material test reports for the assemblys materials; (d) Actual final pressures for each test; (e) Length of time from test initiation t
49、o the time of burst, or the hold time at or above the computed target pressure; (f) Calculations performed; (g) Location of rupture, if any, including a sketch. The test report shall be made available at the manufacturers facility for inspection by the purchaser or regulatory authority. 5. HYDROSTATIC TESTING 5.1 Unless otherwise agreed upon as per Section 2.3, welding fittings shall be capable of withstanding a hydrostatic test pressure as specified in Section 2.2; however, hydrostatic testing by the manufacturer is not required. 6. MATERIALS 6.1 The steel shall b
